Lighting control system



July 31, 1945. F. WILLIS, JR 2,380,486

LIGHTING CONTROL SYSTEM Filed March 11, 1942 2 Sheets-Sheet l INVENTOR.

FLO YD WILL /5 Jr.

'5 BY 025mm,

July 31, 1945. F. WILLIS, JR

LIGHTING CONTROL SYSTEM 2 Sheets-Sheet 2 Filed March 11, 1942 INVENTOR.BY L 0 YD WILL/.5 Jr.

Patented July 31, 1945 UNITED STATES PATENT OFFICE amass arcn'rnvocoN'raor. SYSTEM Floyd wuusjsa, 'lulaa, om.

Application March 11, 1942, Serial No. 434,211

Claims.

This invention relates to control devices for electric illuminatingcircuits and more particularly to an automatic device for opening andclosing circuits such as illumination displays or the automaticdeflecting or dimming o! the headlights of automotive vehicles.

It is commonplace to provide illuminated display devices or signsproximate highways so that such devices are made visible at night to thepassing motorist. Such devices include switching means, either proximateor remote therefrom, whereby the illuminating circuit can be closed andopened so that illumination is provided for desired portions of the dayand night. Such an arrangement, however, requires a constantillumination during the period intermediate the closure and the openingoi the circuit, which interval is usually the period between dusk anddawn. In many instances the illuminating energy is wasted as the displaydevice is in constant operation whether or not the persons for whom thedisplay is intended are proximate thereto.

It is a primary object oi this invention to conserve energy withoutimpairment of results by providing a device whereby an illuminatingdisplay circuit will be closed, or energized, only when a source oflight, such as the headlights of an automotive vehicle, is in thevicinity of the control mechanism for the display.

Even where it is desirable that an illuminating circuit be substantiallyconstantly energized, as in urban areas, occasions arise where it isdesirable to control the circuit instantly as, for example, incompliance with blackout regulations. Such control is frequentlyinconvenient unless the services of a control operator are retained.This invention also comprehends as a further object the provision ofmeans for controlling an illuminating display circuit by means ofradiant energy from a separate circuit which is under constant control.

Another object is to provide a circuit control device which isresponsive to radiant energy and adapted to maintain a circuit closedduring the time that such energy is supplied to the device.

Still another object is to provide a device including an adjustableelectronic delay whereby the opening of the control circuit is delayedby a predetermined amount alter the energizing source of radiant energyhas been removed.

The present invention also comprehends, .and it is an object of theinvention to provide, photoelectric control of vehicle headlightswhereby the dim or depressed headlightbeam is used whenever approachingan oncoming vehicle.

Another object is to provide an automatic headlight dimmer includingmechanism for accelerating the dimming operation when a beam of light issuddenly applied to the device.

The foregoing and other oblects will be more fully apparent i'rom thefollowing description taken in connection with the accompanying drawingsin which:

Fig. 1 is a sectional view through a pick-up unit within which the lightresponsive cell of the device is housed together with other elements ofthe device;

Fig. 2 is a schematic diagram of the circuit utilizing the invention forcontrolling the illumination of a light display or sign;

Fig. 3 is a schematic diagram of a circuit whereby the invention isutilired to automatically control the dimming oi the headlights of anautomotive vehicle.

In Fig. i there is shown a light responsive or pick-up unit l whichconstitutes a portion of the embodiment of the invention. This unit maybe placed in any desired location where it will receive ardiant energyfrom a source which, it is intended, shall effect the operation or thecontrol mechanism. The unit may be located near the circuit to becontrolled or remote therefrom. At-

tention is directed to the iact that this disclosure refer to a lightresponsive device and it is intended by such terminology to include adevice which is responsive to radiant energy both within and without thevisible spectrum.

The unit I comprises the housing 2 having at its forward end an openingI which is preferably elongated in a plane perpendicular to the figureand is provided with a lens t to concentrate light upon an elongatedphotoelectric cell 5 mounted within the housing 2. Other elements of thedevice are also mounted within the housing. as will presently appear,and a multi-conductor cable 8 terminating in a plug i facilitatesintercon nection between the pick-up unit i and the re mainder of theelectric circuit of the control system. I

Reference is now made to Fig. 3 which shows a circuit diagram inaccordance with the invention for controlling the headlights of anautomotive vehicle in a manner that the elevated or bright beam from thefilament I0 is normally lighted. The device is so constructed, however,that a beam of light ialling upon the photoelectric cell 5 will eflectsuch control of the circuit that the filament I0 is extinguished and thedim or depressed beam irom the filament l I will be lighted duringthetime intervalthatthecelllisexcited bythebeam ofiighti'allingthereon.

The complete system of the invention may comprise component units suchas the light responsive or pick-up unit I, a control unit generallyreferred to as II, and a power relaying tmit shown as II. The dottedinterconnections between the units I. II and II are illustrative of thefact that, if desired, these units may be separate and distinct and inspaced relation one to the other. It is to be understood, of course,that the units may be embodied in a single group and enclosed in ahousing if so desired, the illustration being intended primarily tosimplify an understanding of the invention.

The unit I includes the photoelectric cell I and the vacuum tube It. Theheater II of the tube II is heated by an electric currentsupplied from asource, such as the usual vehicle battery, connected to the terminals2!. The plate circuit of the tube It includes a relay II and thiscircuit is supplied from a suitable source of potential connected to theterminals II of the control unit II.

The relay II is normally closed against the upper contact I2 by means ofthe spring It so that a suitable bias, preferably zero, is placed uponthe input grid 34 of the vacuum tube II. This bias upon the grid 34causes a sui'ficient current to iiow in the tube II that the relay II inthe plate circuit of this tube is energized and closes upon the contactI1 against the tensiion of the spring II. Current then flows from theleft terminal 20 to and through the contact 11 and thence through relaysII and I! of the power relay unit II. The energization of the relay I2opens its normally closed contacts II and the contacts II o! relay IIare closed, whereby a current is supplied directly from the terminals 2|to the filament II. This condition exists so long as the current throughrelay II is insuiilcient to close such relay.

Attention is heredirected to the fact that the potential placed upon theinput grid II of the tube .II also .charges the condenser II which isshunted by a resistor ll. Further'reference will be made to the functionwhich these elements perform in the circuit.

If radiant energy, such as a beam of light from the headlight of anoncoming vehicle, falls upon the cell I, the input grid II of the tubell becomes morepositive and the plate current of this tube increases asa result, to actuate the relay ll so that the circuit through thecontact I! is broken and a new circuit through the contact I! is closed.Current then flows from the left terminal II to and through the relay IIof the power relay unit and the relay II whereby the latter ismaintained open while the former is closed upon the contact II. Currentthen fiows from the terminals it through the filament Ii whereby thereis provided a dim or depressed beam of light.

By virtue of the charge placed upon the condenser II. as aboveexplained, the plate current of the tube II does not immediatelydecrease sumciently that the relay II is opened. Hence the filament IIcontinues to be illuminated momentsrily and until the charge on thecondenser II has decreased sufiiciently to permit the relay II to open.For this reason both of the filaments II and I l are momentarilyilluminated, this simultaneous lighting of the filaments temporar ily spplying an intense beam which is instrumental in assuring the actuationof a similar device installed upon an oncoming lighted vehicle.

assasso Another important feature of the invention resides in theutilisation of a condenser ll between the plate of the tube It and theinput grid 84 of the tube II. This condenser ll becomes quickly chargedwhen a surge of current takes place in the plate circuit of the tube IIas when a light is suddenly applied to the photoelectric cell I. Thecharge is such as to overcome the charge on the condenser II and hencesubstantially instantaneous operation of the dimming mechanism takesplace.

During the time the cell I is subjected to a beam of light thecondensers II and I1, connected between the input grid II and thefilament l4, become charged. When the oncoming light beam decreases, bydimming, the charges on these condensers decrease slowly but aresufiicient that the plate current of the tube It maintains the relay IIclosed so that the depressed beam from the filament II is continuouslymaintained although the lights of the oncoming vehicle have been dimmed.This delay in discharge of the con densers II and I1 is augmented by thecircuit which includes the condenser 48 and the resistor 44 which supplya fixed constant delay of the bias initially determined by the resistorII across the terminals of the filament II of the tube II.

An additional important function of the condensers II and I1 is that ofmaintaining the filament ll lighted for a brief interval after theenergizing beam of light has been removed from the cell I. In theabsence of such control the filament II would be lighted the instant thelight beam ceases to fall upon the cell I. Hence in event of successiveoncoming vehicles there would be a complete operation efi'ected from theheadlights of the successive vehicles. By means of the construction Justdescribed the depressed beam is maintained continuously until the excit-40 ing source of light has been removed and a sumcient time for thecharges on the wndensers II and I I-to leak therefrom.

Relay II, to which reference has been made, is an underload relay andserves in case of circuit failure to maintain the filament llilluminated so that the dim or depressed beam is constantly maintainedin event any other portion of the device fails to function.

Reference is now made to the circuit shown in Fig. 2 which is designedto control illuminated displays such as signs, window displays, etc. Itis to be understood-that a unit such as that showninl'lg.1maybeusedandsuchunitmaybe placed where it will be stimulated bythe headlight of an approaching vehicle or in a position to bestimulated by light from existing lighting installations which are underthe constant control of an operator.

In this embodiment a conventional source of electrical energy such asvolts alternating current is supplied to the terminals II, it beinintended that such source shall be utilized to energize the lightingelements II of the display device II. This embodiment of the inventionincludes a current conversion or rectifying unit I! by means of whichsuitable potentials are supplied to the vacuum tube It and thephotoelectric cell I.

The filament II for the heated cathode of the tube II is connected tothe secondary terminals of a transformer II of which the primarywindings are directly connected to the terminals II through conductorsII. The mid point of the secondary windings of the transformer II has adirect connection I1 to the common connection tween the filament 64 andthe plate 15 of the tube 63 and also between the elements of the cell I.The cathode of the cell is directly connected to the input grid 16 ofthe tube 63 and the connection thereto includes a resistor 11 and asecond resistor 18.

The plate circuit of the tube 63 includes a relay 80 having a pair ofswitch blades for contact respectively with terminals BI and 82. Theswitch blades are normally held in open position by a spring 83, itbeing understood that the blades will close upon their respectivecontacts when the relay is sufliciently energized by current flowing inthe plate circuit of the tube 63.

Closure of the upper switch blade with the contact 8| completes acircuit from the terminals 60 and through the relay 90 to effect closurethereof with the terminal 9| so that current is also supplied to theilluminating element 6| of the display device 59.

Closure oi the switch blades of the relay 80 also completes a circuitfrom one terminal of the rectifying unit 62 through a resistor 92 to theconductor 61, a condenser 93 being interposed between the remote ends ofthe resistors 18 and 92. By reason of this construction the condenser 93becomes charged whenever the relay 80 is actuated by a beam 01 lightstriking the cell 5.

The operation of the circuit is believed apparent from the foregoingdescription. By wav of summary, it may be stated that light strikin thephotoelectric cell 5 from a vehicle headl g t. a controlled highwayilluminator, or other source of light causes the input grid 16 to becomesufilciently positive that current flowing through the relay 80increases and operates the relay. As already explained, the closure ofthe relay energizes the relay 90 whereby energy from the terminal 60 issupplied directly to the elements 6| oi the display device 59 on whichthe illumination is to be controlled and such elements will remainlighted until the relay 80 has again opened.

As already pointed out, the condenser 93 becomes charged during theperiod the cell is stimulated and the lights 6| remain in operation.Hence the bias is placed upon the input grid 16 of the tube 63.

If the cell 5 is excited from the headlights of a motor vehicle theamount of light decreases as the vehicle passes adjacent the cell. It isdesirable, however, that for maximum efficiency the elements 6| remainlighted for a short period thereafter both to improve the continuity ofthe illuminated displays and also to avoid successive operations of thedevice in event a second source of light is about to move within theoperating range of the device. This condition is made possible by thecharge on the condenser 93 which leaks slowly therefrom through theresistors 92 and 18. When this charge upon the condenser has decreasedto a certain point the bias upon the input grid 16 has loweredsufficiently that the plate current through the relay 80 falls andpermits the relay to open, whereupon the relay 90 also opens and thelight 6| is extinguished.

Broadly, the invention comprehends new and useful improvements incontrol devices for illuminating circuits, and in particular for theopening and closing of such circuits in response to radiant energy.

I claim:

1. In a device for the control of vehicle headlights the combination of,separ te filaments to be'energized, a source of energy for saidfilaments, means normally closing a circuit from said source to one ofsaid filaments, and means responsive to radiant energy for deenergizingsaid one fila- I ment and energizing the other of said filaments fromsaid source, said last mentioned means including means for maintainingsaid one filament energized for a predetermined period after the secondfilament is energized.

2. In a device for the control of vehicle headlights the combination of,separate filaments to be energized, a source of energy for saidfilaments, means normally closing a circuit from said source to one ofsaid filaments, means responsive to radiant energy for deenergizing saidone filament and energizing the other of said filaments from said sourceand for thereafter deenergizing the second filament and reenergizing thefirst filament when stimulating radiant energy is removed, said lastmentioned means includin electronic means for delaying saiddeenergization and reenergization for a predetermined interval after thestimulating radiant energy is removed.

3. In a device for the control of vehicle headlights the combination of,separate filaments to be energized, a source of energy for saidfilaments, means comprising a grid-controlled vacuum tube and a relaynormally closing a circuit from said source to one of said filaments,means normally maintaining a bias on the grid of said tube meansresponsiv to radiant energy for energizing the other of said filaments,and means for controlling the grid bias on said tube to hold said relayclosed for a predetermined time after said other fila= ment isenergized.

4. In a device for the control of vehicle headlights the combination of,separate filaments to be energized, a source of energy for saidfilaments, means comprising a grid-controlled vacuum tube and a relaynormally closing a circuit from said source to one of said filaments,means normally maintaining a bias on the grid of said tube meansresponsive to radiant energy for energizing the other of said filaments,means for controlling the grid bias on said tube to hold said relayclosed for a predetermined time after said other filament is energized,and additional means for overcoming said bias when a beam of light issuddenly applied to the energy responsive means.

5. In a device for the control of vehicle headlights the combination of,separate filaments to b energized, a source of energy for saidfilaments, means normally closing a circuit from said source to one orsaid filaments, means responsive to radiant energy for energizing theother of said filaments, means for deenergizing said one filament at apredetermined time interval after the other is energiz d, and additionalmeans for decreasing the time interval when a beam of light is suddenlyapplied to the energy responsive means.

FLOYD WILLIS, JR.

